That context is more important than you are giving credit for. I don't think it's that they are behind as performers, but they are going for something entirely different. Saying they are bad compared to american performers is like saying chocolate ice cream really sucks at being a chocolate bar. Of course it does, because it's meant for a similar purpose (enjoyment in some manner) but a very different experience. If you had a situation that called for ice cream and you got a chocolate bar, that would suck there. That is the sort of thing going on in context of the music, performance style, cultural difference, and expectations of the minds of american listeners.
See, this is what I'm talking about. I enjoy this just fine, but the claim insinuated is so absurd to me. How can knowledge of music and all the ways it is performed and enjoyed be so limited?
the pretension is hilarious